Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

H, W = map(int, input().split())
edges = ['#']*(W+2)
field = [edges]
dyx = [(0, 1), (0, -1), (1, 0), (-1, 0)]
bk = 0
for _ in range(H):
    line = list(input())
    bk += line.count('#')
    field.append(['#'] + line + ['#'])
field.append(edges)

steps = 1
q = deque()
field[1][1] = 1
q.append((1, 1, 1))

while q:
    cy, cx, lv = q.popleft()

    for dy, dx in dyx:
        ny, nx = dy+cy, dx+cx

        if field[ny][nx] == '.':
            field[ny][nx] = lv+1
            q.append((ny, nx, lv+1))
steps = str(field[H][W])
if steps.isnumeric():
    print(W*H-bk-int(steps))
else:
    print(-1)